Tuning coil



M. OSNOS TUNING COIL Filed Dec.

May 22, 1934.

W 22rd U m n sgxljfgg a INVENTOR MENDEL OSN 5 BY ATT ORNEY Patented May 22, 1934 UNITED STATES PATENT OFFICE,

TUNING COIL Mendel Osnos, Berlin, Germany, assignor to Telefunken Gesellschaft fur Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application December 6, 1932, Serial No. 645,938 In Germany November 10, 1931 9 Claims. (01. 175-359) This invention relates to an improved tuning coil arranged so that the self inductance whose dependency 'on the temperature is adjustable as may be desired, or controlled respectively as may be desired, or totally or approximately eliminated.

The self induction of a copper coil generally increases with increasing temperature. For a coil as shown for instance in Figure 1 for which D O E X (see Rein-Wirtz Radiotelegraphisches Praktiktikum 1921 3d edition, page 128) the self induction is approximately wherein N=total number of turns D=average diameter of the coil in cm. U=2 (l+b) and since It can be seen from Equation 3 that the self induction of the coil is proportional to the value. of l+at.

According to the present invention the dependency on the temperature t of the self induction of a coil can be made adjustable or controllable respectively as may be desired. The invention affords in particular to render the self induction totally or approximately independent of the temperature. This is accomplished by determining the distance between the individual elements of a part of the coil by one or several members the heat expansion coefficient of which is greater than the heat expansion coefficient of copper or the electric conductor of the coil respectively.

The correctnessof the inventive idea will now be proven on hand of Equation 1. a

For the sake of simplicity it is assumed that b is much smaller-than I so that 55 can be neglected.

According to the invention the length l of the coil is determined by a suitable retaining member, the expansion coefficient of which may be generally taken as being It times greater than the expansion coeflicient of copper so that: 00

1:1,(1+Ka) (4) Therefore 4 (1+ r L=L (1+ Kat) (5) on As compared with Z the value a t is generally small so that:

1+at) ;1+ 50d --(6) 4 I+5at ov m If the retaining member determining the dimension Z is formed of hard rubber whose heat expansion coeflicient is 5 times as great as for copper the following is obtained:

therefore totally independent of it.

If however a member is used having an expansion coefficient which is greater than that of hard rubber as for instance zelluloid with K ='6,6 then and therefore L L,, (9) Coils for which the value of I is between 1 and 3 behavestill more favorably since, as is known the following equation is approximately correct L=10,5XN D cm (1o) and it is therefore approximately Lilii 1 which shows that the separator determining the length of the coil must have an expansion coeflicient K a=3oz in order that being composed of insulating material having a high heat expansion coeflicie'nt.

2'indicates' an expansion type spring copper coil. 3 shows a bolt of the same or similar insulating material as for retaining member 1 above mentioned.

1 4 refers to the bolt rod having a threaded portion and also indicates a variable condenser in parallel with the conductor turns.

5 is a nut formed of the same or similar material as used for members 1, or 4.

6 designates round caps or elongated press discs of insulating material, as also shown in Figure4.

7 are intermediate layers of insulating mate- .rial suitably of a similar characteristic as 1 and 4 and 8 represents elastic rubber rings.

According to Figures 2 and 3 only a part of the coil which is about one half of its length is somewhat compressed by the retaining members against the springy force of the windings so that the distance (a) between the outer windings of this retained part is always determined by the retaining members or separator. If the retaining members should expand due to the heat, the distance (a) between the outer windings becomes greater, and the self induction of this retained part of the coil is correspondingly reduced. If, however, the retaining members shrink due to the cooling off, the retained coil distance becomes smaller and the self induction willincrease in the same proportion.

From Figure 3 can be seen that the part of the.

coil retained between the separators as well as the space between the conductor windings of this part of the retained coilcan be very finely ad-' justed in any. desired way.

The embodiment according to Figure 4 is .litable for coils having acomparatively large rumber of conductor turns. In this case suitable insulating material 7 is provided between the intermediate insulation 7 and the retaining bolt 4, it is advisable to compensate the distance. determined by the retaining bolt or separator 4 by a substantial springy force for instance by a rubber ring 8 interposed between the round end caps 6 and the intermediate insulation 7, 6

It may under certain conditions be of advantage to connect the self inductance of the present invention in series, or parallel to ordinary nontemperature controlled self inductances, in order to vary the dependency of the resulting self inductance on the temperature-in any desired manher, or to cause this dependency to follow any desired law, respectively. In order to obtain the result mentioned, various parts of a coil can also be provided with insulating separators. of various materials having different expansion coeflicients or coils provided with various insulating separators may be combined.

I claim:

1. An inductance coil having a self inductance which is controlled by insulating material, a plurality of retaining members having a high heat expansion coeflicient, some of said members disposed in the space between the individual conductor turns so that the total length of the coil is determined by a distance of said retaining I members.

2. In aninductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes, said means comprising a plurality of retaining members of insulating material having hook-like ends located outside the inductance coil, said-coil having conductor'turns composed of metal having spring-like characteristics.

3. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductor turns of spring-like metal, a plurality of insulated members for retaining a portion of the conductor turns on said coil, said insulated retaining members having hook-like ends to secure the conductor turns in proper spaced relation.

4. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductor turns of spring-like metal, a plurality of members for retaining a portion of the conductor turns on said coil, said retaining members comprising two insulated discs of a larger outside diameter than said coil, 2. central insulatedmember passing through the said coil and the said dividual conductor turns. ,The insulation mate-' discs rial parts 4 and 7 expand due to the heat which in turn reduces the self induction of the coil.

During the cooling off of the coil the insulation material shrinks. This alone would however not be sumcient in order to contract the total coil. This is being accomplished by-, the bolt 3, 4, and nut 5 which determines the space between the outer windings of the coil. when the cooling ofl. occurs the bolt and accordingly the coil contracts and the self induction is thereby effected in the sense ofthe contraction.

Fig. 4 also indicates a variable condenser arranged in parallel with the retained conductor turns of coil so as to provide a tuned circuit.

It is desirable to choose the bolt and the intermediate insulating layer 7 from the same material. In order to balance eventual difierences between the heat expansion coeflicient of the in- 5. In an inductance coil whose inductance is subject to changes'by temperature variations, means for controllingsaid inductance changes comprising a coil having a plurality of conductor turns of spring copper, a plurality of insulated members for retaining a portion of the conductor turns on said coil, said retaining members comprising two insulated discs of a larger outside diameter than said coil, 'a-central insulated member passing through the said coil and the said discs.

6. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductorrturns of spring-like metal, a plurality of members for retaining a portion of the conductor turns on said coil, said retaining members comprising two insulated discs of a larger outside diameter than said coil, a central adjustable insulated member passing through the said coil and the said discs.

'1. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductor turns of spring-like metal, a portionoi said coil being retained and another portion of said coil being free, a plurality of insulated members for retaining the retained portion of said coil, said insulated retaining members having hooklike ends to secure the conductor turns in proper spaced relation.

8. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductor turns of spring-like metal, a plurality of members for retaining a portion of the conductor turns on said coil, said retaining members comprising two insulated discs of a larger outside diameter than said coil, said discs having an outer rim, an insulating member interposed between each of said conductor turns, and an elastic compression and expansion member at each end or the coil located within the rims of said discs and said insulating member. a

9. In an inductance coil whose inductance is subject to changes by temperature variations, means for controlling said inductance changes comprising a coil having a plurality of conductor turns of spring-like metal, a plurality of members for retaining a portion of the conductor turns on said coil, said retaining members comprising two insulated discs of a larger outside diameter than said coil, said discs having an outer rim, an insulating member interposed between each of said conductor turns, an elastic compression and expansion member at each end of the coil located within the rims of said discs and said insulating member, and a variable condenser arranged in parallel with said conductor turns so as to provide a tuned circuit.

'MENDEL OSNOS. 

